printk: fix typo in printk_safe.c

Link: http://lkml.kernel.org/r/1508682655-27293-1-git-send-email-bhe@redhat.com


Cc: rostedt@goodmis.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Baoquan He <bhe@redhat.com>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>